Attic insulation, air sealing, crawl spaces and walls for homes in Wentzville — starting with a free assessment that measures the R-value you actually have. The typical home here dates to the late-2000s, and 1% of its 16,601 homes went up before 1940.
Wentzville runs to about 21 square miles and roughly 48,646 people. It sits about 35 miles west of downtown St. Louis. That is roughly 16,601 housing units. The community dates back to 1855. We cover ZIP code 63385.
Our job history shows nothing in Wentzville so far. Plenty of sites will show you a number here anyway.
The typical home in Wentzville dates to around the late-2000s. Houses this new were built to an energy code, so the attic usually started at something close to the required depth. What goes wrong here is settlement, gaps at the eaves, and a ceiling plane nobody ever sealed.
Wentzville was Missouri's fastest-growing city by percentage from 2000-2020, expanding from 7,058 to 44,372 residents, so the large majority of its housing stock is 21st-century new construction.
That includes Bear Creek. Housing age and construction shift across Wentzville, sometimes by decades within a few streets, which is why we look in the attic before quoting rather than after.
The Census Bureau estimates 16,601 homes in Wentzville. 104 of them (1%) went up before 1940 — 39th of 44 places on this site for pre-1940 housing. The 2000s were the busiest decade, adding 6,855 of today's homes (41%); 10% predate 1980 and 81% were built in 2000 or later. For St. Charles County as a whole the pre-1940 share is 2%, so Wentzville sits below it.
Of 16,294 occupied homes, 63% heat with utility gas and 34% with electricity; another 2% burn propane or other tank gas. Electric heat here is more common than across the county (30%), and ranks 22nd of 44 on this site. Which utility program can contribute depends on the heating fuel and on who sends the bill, so that is the first thing an assessment pins down.
82% of occupied homes are owner-occupied and 82% of all homes are single-family detached houses. With houses like these, the conversations we expect most are about air sealing on newer houses that already have depth and an energy assessment before deciding what to fix first.
| Built | Homes | Share | |
|---|---|---|---|
| Before 1940 | 104 | 1% | |
| 1940s | 107 | 1% | |
| 1950s | 734 | 4% | |
| 1960s | 341 | 2% | |
| 1970s | 350 | 2% | |
| 1980s | 417 | 3% | |
| 1990s | 1,062 | 6% | |
| 2000s | 6,855 | 41% | |
| 2010s | 6,023 | 36% | |
| 2020 or later | 608 | 4% |
16,601 homes, Census ACS 2020–2024 (B25034, B25040, B25003); 16,294 occupied.
13,486 of Wentzville's 16,601 homes (81%) were built in 2000 or later. Depth is rarely what is missing in houses this new; air paths are: attached garages, bonus rooms over them, the chase around a high-efficiency flue, and the thin edge where blown fiber meets the wall plate. They usually earn their money back on sealing rather than on more fiber.
Wentzville does not publish the energy code edition it enforces, so this page does not name one. The city's Building Codes page lists the codes it enforces with local amendments: 2021 IBC at Sections 500.030 and 500.060, 2021 IRC at Sections 500.070 and 500.080, 2021 IPMC, 2021 IFGC, 2021 IPC, 2021 IMC and the 2020 National Electrical Code. No International Energy Conservation Code appears anywhere on that list. Across this metro the adopted editions run from the 2015 IECC to the 2024 IECC, and several jurisdictions have no energy code at all, which is a wide spread. Ask which one your contractor is building to.
There is no published answer for Wentzville. Neither the permit-required list nor the exemption list mentions insulation or air sealing at all. The building permits page says building permits are required to construct, modify and in some cases repair a structure, and lists accessory buildings and sheds, decks and patio covers, driveways, fences, finished basements, pools and hot tubs, electrical, plumbing and HVAC work, retaining walls over 4 feet, sewer and water work, solar panels, remodels and additions. Insulation, weatherization and air sealing are not on that list. That silence is not permission and it is not a prohibition. We settle it with a phone call before the crew is scheduled.
The published number is 636-327-5101. The department page is here.
Permitting is on us, not on you.
Wentzville is on the Missouri side, where most addresses buy their electricity from Ameren Missouri. Its Pay As You Save program publishes $0.20 per square foot on ceiling and attic insulation and $0.06 per square foot on air sealing for the 2026 program year; the incentive comes off the cost and the rest is repaid through a monthly charge on the bill. The conditions: an attic going from R-20 or below to at least R-38, air sealing that cuts measured leakage by 20 percent, and twelve months in the home. CommunitySavers can include attic insulation at no charge for income-eligible households. Income-qualified households can apply to North East Community Action Corp. (NECAC) (573-324-2231) for free weatherization instead. For every condition attached, see the St. Charles County page or the rebate guide.
Every layer of an insulated attic, explained
Elsewhere in St. Charles County we also cover:
Missouri sets none of this at state level. Across the 6 places in this table there are 3 different adopted editions (2015 IECC, 2021 IECC and 2021 IRC ch. 11), and none of the 6 publishes a permit rule for insulation.
| City | Energy code | Attic R required | Permit to insulate | Building dept. |
|---|---|---|---|---|
| Wentzville | Not published | — | Not published | 636-327-5101 |
| Cottleville | 2021 IRC ch. 11 | R-38 | Not published | 636-498-6565 |
| Lake St. Louis | 2015 IECC | R-49 | Not published | 636-625-1200 |
| O'Fallon | 2021 IECC | — | Not published | 636-379-5660 |
| St. Charles | 2015 IECC | R-49 | Not published | 636-949-3200 |
| St. Peters | 2021 IRC ch. 11 | R-38 | Not published | 636-477-6600 ext. 1670 |
All 6 St. Charles County jurisdictions side by side →
Wentzville does not publish the energy code edition it enforces, so we do not state a required figure here. The Department of Energy recommends R60 for an uninsulated attic in this climate zone and R49 where there are already a few inches.
Wentzville has not published a rule for it; the building department at 636-327-5101 is called before the job starts.
Ameren Missouri's Pay As You Save: $0.20 per square foot for an attic starting at R-20 or below and $0.06 per square foot for air sealing in 2026, with the balance on the electric bill. The federal 25C credit ended for work placed in service after December 31, 2025.
The typical home in Wentzville dates to around the late-2000s; the Census Bureau's 2020-2024 median year built is 2008. Of its 16,601 homes, 1% went up before 1940 and 81% in 2000 or later. It is a median for the place, not a survey of individual houses.
Code and permit facts checked September 10, 2026, rebates October 24, 2026; housing: Census ACS 2020–2024. Sources: wentzvillemo.gov (2, 3) · library.municode.com · en.wikipedia.org · city-data.com · bearcreekwentzvilleneighborhood.org · ameren.com (2, 3, 4) · energystar.gov · data.census.gov. These change; confirm with the building department at 636-327-5101 or your electric utility first.
Free assessment: what depth you have now, what it has settled to, and what the sealing is worth.
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